Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
  • BCO-DMO Processing Description
• Related Publications
• Related Datasets
• Parameters
• Instruments
• Project Information
• Funding

This data is from a flume experiment undertaken at Friday Harbor Laboratories in July 2023 as part of a project investigating how the metabolic activity of marine organisms can alter the water chemistry of their interstitial spaces, and how these microscale alterations affect interactions in coastal ecosystems. 

This dataset presents:

1. Bulk seawater chemistry measurements using HOBO loggers for dissolved oxygen, pH/Temp, and Conductivity
2. Interstitial water chemistry measurements using Pyroscience microsensors for oxygen, pH, and temperature

Additional data on velocity and turbulence measurements using a Nortek Vectrino can be viewed at https://www.bco-dmo.org/dataset/982717 (see also Related Datasets section below).

A flume experiment was conducted at Friday Harbor Laboratories where flow and chemical gradients were measured within and above a dense aggregation of mussels (Mytilus trossolus). Four experimental flume speeds were examined: Q=quarter inch per second, H=half inch per second, O=one inch per second, and OH=one and a half inches per second. Data collection occurred over five days (July 24-28th, 2023) with a complete set of profiles measured at each background speed (n=4) every day. This led to a total of 20 profiles taken at 5 mussel bed locations, including 5 replicates of chemistry profiles and 3 replicates of velocity profiles at each of the background speeds: 0.25, 0.5, 1, 1.5 inch/sec or 0.6, 1.3, 2.5, 3.8 cm/sec respectively. A background velocity in inches was initially used because this was how the flume’s motor was set up.

Bulk seawater chemistry sensors consisted of a collection of Onset HOBO loggers. A dissolved oxygen (U26-001), pH/Temperature (MX2501) and Conductivity (U24-002-C) logger were used to measure ambient water chemistry in the experimental flume during the trials. The array of three loggers were bound with a zip tie and placed at the downstream end of the flume’s working section at a depth of approximately 5 cm. 

Interstitial seawater chemistry was measured with a collection of Pyroscience microsensors. A micro-oxygen (OXROB10-CL4), pH (PHROBSC-PK8T), and temperature sensor (TSUB21) were used in tandem to quantify water chemistry within the interstitial spaces of a mussel bed. The three sensors were connected to a Firesting-PRO 2-channel, a compact USB-powered fiber-optic meter which was further connected to a laptop for data collection. The meter has an internal pressure sensor (mbar) that measures atmospheric pressure and automatically compensates for oxygen values. The measuring frequency was set to  one second (1s) for all sensors. Both the pH and DO probes required calibration. For the oxygen probe, a 2-point calibration was performed with 100% and 0% air saturation. The 0% calibration came factory completed, so only the 100% calibration was performed. A small flask of experimentally relevant water (local seawater) had an air stone placed into it for 15 minutes to reach 100% air saturation, and then a calibration was performed according to the instrument manual. For the pH probe, a 2-point calibration was performed using Pyroscience pH tablets that were combined with 100mL of DI water to create standards of pH 2 and pH 11 for calibration, as stated in the instrument manual.

Data frequency was once per minute for HOBO measurements and once per second for Pyroscience measurements so columns where second by second data wasn't important for analysis have missing data due to difference in measurement frequency between the sensors. Data filled for HOBO pH was linearly interpolated in order to allow for second by second comparison of water chemistry parameters.

For both the Pyroscience (interstitial) and HOBO (ambient) dissolved oxygen sensors, the raw values were adjusted for the measured salinity. These values are labeled DO Adj. conc in the datasets. For the HOBO data, processing was done using HOBOwarePro and the raw data from the conductivity sensor. For the Pyroscience data, processing was done in the Pyroscience Data Inspector and an average salinity of 27.5 ppt was used for the measurements as this was the average salinity of the week and the salinity ranged from 27.3 - 27.6 ppt which creates an insignificant difference in the oxygen adjustment (less than 0.01). 

- Imported data from source files: VPH_Complete.xlsx, VPOH_Complete.xlsx, VPO_Complete.xlsx, VPQ_Complete.xlsx, VP2H_Complete.xlsx, VP2OH_Complete.xlsx, VP2O_Complete.xlsx, VP2Q_Complete.xlsx, PH_Complete.xlsx, POH_Complete.xlsx, PO_Complete.xlsx, PQ_Complete.xlsx, P2H_Complete.xls, P2OH_Complete.xlsx, P2O_Complete.xlsx, P2Q_Complete.xlsx, VP3H_Complete.xlsx, VP3OH_Complete.xlsx, VP3O_Complete.xlsx, VP3Q_Complete.xlsx,
- Concatenated all files into a single CSV file
- Combined Date and Time columns for both Pyro and HOBO dates.
- Added new columns for Day_of_Week and removed HOBO Day
- Added new column for Trial
- Sorted by Pyro_Date

NSF Award Abstract:
The project investigates how the metabolic activity of dense aggregations of marine organisms alter the water chemistry of their interstitial spaces, and how these microscale alterations feedback to affect the organisms’ interactions in coastal ecosystems. The research team focuses on bivalve mussels, foundation species that form dense ‘beds’ typically known for facilitating other species by ameliorating harsh flow conditions. This ability can become a liability, however, if flow is not sufficient to flush the interstitial spaces and steep, metabolically-driven concentration gradients develop. The research evaluates whether corrosive chemical microclimates (such as low oxygen or low pH) are most extreme in low flow, high temperature conditions, especially for dense aggregations of mussels with large biomass and/or high respiration rates, and if they negatively impact mussel beds and the diverse biological communities they support. The research addresses a global societal concern, the impact of anthropogenic climate change on coastal marine ecosystems, and has potential applications to aquaculture and biofouling industries by informing adaptation strategies to “future-proof” mussel farms in the face of climate change and improved antifouling practices for ships, moorings, and industrial cooling systems. The project forges new collaborations with investigators from three campuses and integrates research and education through interdisciplinary training of a diverse group of graduate, undergraduate and high school students. STEM education and environmental stewardship is promoted by the development of a K-12 level science curriculum module and a hand’s-on public exhibit of bivalve biology at a local shellfish farm. Research findings are disseminated in a variety of forums, including peer-reviewed scientific publications and research presentations at regional, national and international meetings.

The research team develops a framework that links environmental conditions measured at a coarse scale (100m-100km; e.g., most environmental observatories) and ecological processes at the organismal scale (1 cm – 10 m). Specifically, the project investigates how aggregations of foundation species impact flow through interstitial spaces, and how this ultimately impacts water chemistry immediately adjacent to the organisms. The research focuses on mytilid mussels, with the expectation that the aggregation alters the flow and chemical transport in two ways, one by creating a physical resistance, which reduces the exchange, and the other by enhancing the exchange due to their incurrent/excurrent pumping. These metabolically-driven feedbacks are expected to be strongest in densely packed, high biomass aggregations and under certain ambient environmental conditions, namely low flow and elevated temperature, and can lead to a range of negative ecological impacts that could not be predicted directly from coarse scale measures of ambient seawater chemistry or temperature. The team develops computational fluid dynamic (CFD) models to predict interstitial flows and concentration gradients of dissolved oxygen and pH within mussel beds. The CFD model incorporates mussel behavior and physiological activity (filtration, gaping, respiration) based on published values as well as new empirical work. Model predictions are compared to flow and concentration gradients measured in mussel aggregations in the laboratory and field. Finally, the team conducts several short-term experiments to quantify some of the potential negative ecological impacts of corrosive interstitial water chemistry on mussel aggregations, such as reduced growth, increased dislodgement, increased predation risk, and reduced biodiversity. Because the model is based on fluid dynamic principles and functional traits, the framework is readily adaptable to other species that form dense assemblages, thereby providing a useful tool for predicting the ability of foundation species to persist and provide desirable ecosystem services under current and future multidimensional climate scenarios.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.